1. Field of the Invention
The present invention relates to an improved locking device for luggage trolleys.
2. Description of the Related Art
A typical collapsible luggage trolley includes a pair of outer tubes, a pair of inner tubes telescopically received in the outer tubes, respectively, and a handle securely connected to upper ends of the inner tubes. FIG. 6 of the drawings illustrate a prior art locking device for luggage trolleys which includes a rod 60 mounted in an inner tube 400 which, in turn is telescopically mounted in an outer tube 40. A positioning tube 50 is mounted between the inner tube 400 and the outer tube 40 and is threadedly engaged with the inner tube 400 to move therewith. The positioning tube 50 includes a bottom board 52 on which a latch block 62 is slidably mounted under the action of a spring 64. An actuating block 61 is glued to a lower end of the rod 60 to move therewith. When the press rod 60 is pushed downwardly under operation of a handle (not shown) connected to an upper end thereof, an inclined surface 610 of the actuating block 61 bears against an inclined surface 620 of the latch block 62 and thus causes a latch end 63 of the block 60 to disengage from one of a number of openings 41 defined in the outer tube 40 to thereby allow position adjustment of the inner tube 400 relative to the outer tube 40. After completion of such adjustment, the rod 60 is released, and the latch end 63 of the latch block 62 is re-engaged with another opening 41 of the outer tube 40 under the action of the spring 64. Nevertheless, such a positioning device is too complicated and thus is inconvenient and time-consuming to assemble. In addition, it is difficult to disengage the latch block 62 from the outer tube 400 as the friction between the blocks 61 and 62 and between the block 62 and the bottom board 52 is relatively large. Further, the actuating block 61 is adhered to the press rod 60 by glue and thus may fall off the press rod 60 after a period of time.
FIG. 7 of the drawings illustrates another prior art locking device for collapsible luggage trolleys in which the outer tube 70 includes a longitudinal rack 71 formed on an inner periphery thereof, and a gear 73 is rotatably mounted to the inner tube 72. A block 75 is connected to a lower end of a rod 74 operable by a handle button 79. The button 79 is mounted to a handle 78 which, in turn, is mounted to upper ends of the inner tubes 72. When the button 79 is pressed, the block 75 is lifted upwardly and thus disengaged from the gear 73 to thereby allow movement of the gear 73 along the rack 71 for adjusting position of the inner tube 72 relative to the outer tube 70. When the button 79 is released, the block 75 is moved downwardly under the action of a spring 76 to engage with the gear 73 and thus position the inner tube 72. Yet, mounting of the gear 73 onto the inner tube 72 is inconvenient and time-consuming. In addition, the wall thickness of the inner tube 72 is relatively thin and thus may be damaged by the gear shaft 73'. Further, the gear 73 must be processed with high precision, which is also inconvenient and time-consuming as well as costly.
The present invention is intended to provide an improved locking device which mitigates and/or obviates the above-mentioned problems.